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Tough New Spuds Take on Double Trouble / March 2, 2010 / News from the
USDA Agricultural Research Service

Five new potato breeding lines now being tested by
ARS scientists and collaborators could provide the basis for varieties that can
handle powdery scab and black dot diseases. Photo courtesy of Microsoft
Clipart

Tough New Spuds Take on Double Trouble

Americans love potatoes, consuming
about 130 pounds per person annually. But it's a wonder the spuds even make it
to the dinner table, given the many fungal diseases that attack the tuber
croppowdery scab and black dot among them.

Now, five new potato breeding lines being tested by
Agricultural Research Service (ARS)
scientists and collaborators could open the door to new varieties of the crop
that resist powdery scab and black dot diseases, caused by the fungi
Spongospora subterranea and Colletotrichum coccodes,
respectively.

These fungi often occur together in the same soil, attacking the potato
plant's roots, tubers or stems. Outbreaks can cause yield losses of up to 25
percent and prevent tubers from reaching the sizes needed by the french fry and
fast-food industry. Of the two fungi, only black dot can be chemically
controlled with fungicides; however, multiple applications are needed,
ratcheting up production costs to prohibitive levels. A more sustainable
alternative is genetic resistance, according to geneticist
Chuck
Brown, with the ARS
Vegetable
and Forage Crops Production Research Laboratory in Prosser, Wash.

In studies conducted there since 2004 with Washington State University professor
Dennis
Johnson, assistant Tom F. Cummings and postdoctoral associate Nadav Nitzan,
Brown screened an existing collection of wild and cultivated potatoes for
sources of natural resistance to powdery scab and black dot in a local grower's
infested field.

The effort ultimately led to five advanced potato breeding lines that had
been developed from a wild species from Mexico, Solanum hougasii, and a
recent commercial release, Summit Russet. In three years of field trials in
Washington State and Idaho, the potato breeding lines consistently showed fewer
disease symptomsroot galling for powdery scab and sclerotia-infected
stems for black dotthan other lines and varieties tested.

The potato breeding lines themselves aren't intended for production.
Instead, they'll be made available as seed for use in breeding programs aimed
at developing the first commercial varieties with dual resistance to the fungal
diseases, according to Brown, who discussed the research at the 48th Annual
Washington State Potato Conference in January.

The research findings have been published in the journal Plant Disease.

ARS is the principal intramural scientific research agency of the
U.S. Department of
Agriculture (USDA). This research supports the USDA priority of promoting
international food security.